Trap apparatus with bypass

ABSTRACT

Trap muffler apparatus with bypass to a common reactive acoustic element is disclosed. Bypass structure varies from external bypass to a common acoustic element to annular bypass of the ceramic filter to axial bypass through the middle of an annular ceramic filter. Forward or reverse regeneration are possible. Bypass to atmosphere without filtration is avoided with dual in-line traps or with the segmented trap and control of exhaust gases to traps not being regenerated.

FIELD OF THE INVENTION

The invention is directed generally to trap devices and trap mufflerdevices for vehicles, primarily vehicles powered by diesel engines. Thedevice has an internal bypass so that exhaust gases can be directedaround a regenerating trap.

BACKGROUND OF THE INVENTION

Current trap mufflers (e.g., U.S. Pat. No. 4,851,015) provide for trapregeneration and, during regeneration, have an external bypass whichexhausts through an alternative muffler to atmosphere or through analternative trap muffler system to atmosphere. The problem is that trapfilters become clogged and must be periodically regenerated by burningor oxidizing the particulates captured therein. For regeneration systemshaving electrical heaters, there is insufficient vehicle electricalenergy to create sufficient continuing heat to maintain regeneration ifexhaust continues to flow through the trap during regeneration withoutmajor additions to the electrical system. (Some systems, e.g., burners,are capable of providing sufficient heat without bypass.) In addition,current systems bypass into additional devices. Thus, current systems,although effective in a laboratory setting, are very bulky and somewhatcomplex when installed to provide a complete vehicle capability.Reduction in size and complexity results in less cost, weight, etc., andis clearly desirable. The present invention addresses this problem.

Additionally, regeneration of current trap filters proceeds in a forwarddirection from upstream nearest the engine to downstream nearestatmosphere. The filters load more greatly at the downstream end. As aflame front during regeneration proceeds, on many systems it may notcompletely oxidize particulate build-up at the downstream end and, overtime, the filter may become clogged or on a, following regeneration,burn with extreme temperatures to the point of damaging the filter. Thepresent invention provides an advantageous concept for internal bypasswhich furthermore allows reverse regeneration starting at the downstreamend where the greater particulate build-up exists and proceeding towardthe upstream end.

Many other features of the invention which address these and otherproblems with current systems will become apparent hereinafter.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus for processing exhaustgases from an engine. The apparatus includes a housing with first andsecond flow paths for exhaust gases flowing in a forward direction withrespect to inlets upstream and outlets downstream. An acoustic elementis located within the housing for attenuating the sound of the exhaustgases along both the first and second flow paths. The housing has afiltering mechanism for filtering particulates from the exhaust gases. Avalve mechanism diverts the exhaust gases between the first and secondflow paths so that the filtering mechanism can be bypassed when itbecomes loaded.

The filter mechanism may have any of many possible forms. In whicheverform, the filter mechanism is advantageously bypassed internally orexternally of the housing, while utilizing a common acoustic element sothat secondary muffler housings are not needed. An internal bypass canbe along a path about an outer side of the filtering mechanism or alonga path through the filtering mechanism. A path passing through thefiltering mechanism in accordance with the present inventionadvantageously can include a first cylindrical tube fixed with respectto one of the lines leading to the inlet and the outlet of the housingand a second cylindrical tube fitting in sliding circumferentialrelationship with respect to the first tube. Both tubes have openings.Preferably, the tubes have openings upstream from the filteringmechanism and downstream from it such that a rotation of the second tubecauses a valve action as the openings of the tube move into and out ofregistration with one another. As will become apparent, exhaust gaseseither can be directed through the filtering mechanism or can bypass it.With such assembly appropriately controlled regeneration can take placein either forward or reverse directions relative to the flow directionof the exhaust gases.

The present invention provides many conceptual alternatives which leadto more compact and less complex vehicular systems as compared topreviously known systems. The various alternatives and advantages aredescribed in detail hereinafter and provide direct reference to thedrawings now briefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of trap muffler apparatus providingfor external bypass of the trap;

FIG. 1A is an alternate embodiment of apparatus shown in FIG. 1;

FIG. 2 is a schematic illustration of trap muffler apparatus providingfor internal bypass of the trap;

FIG. 2A is an alternate embodiment of apparatus shown in FIG. 2;

FIG. 3 is a cross-sectional view of trap muffler apparatus with anannular trap and an axial tubular shutter valve assembly with aschematic representation of regeneration mechanism in accordance withthe present invention;

FIG. 4 shows the same apparatus as FIG. 3 with arrows illustratingreverse regeneration and exhaust gas bypass of the trap;

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 3;

FIG. 6 is a cross-sectional view of a portion of the annular trap ofFIG. 3;

FIG. 7 is an illustration of a trap loading with particulates;

FIG. 8 is a cross-sectional detail view of a portion of FIG. 3 ofmechanism for mechanically switching the tubular shutter valve assemblybetween open and closed positions;

FIG. 9 is a cross-sectional detail view of an alternate embodiment of anupstream end of the tubular shutter valve assembly;

FIG. 10 is a flow chart illustrating a method of regenerating trapmuffler apparatus having valves upstream and downstream of a trap;

FIG. 11 is a cross-sectional view of trap muffler apparatus similar toFIGS. 3 and 4 except showing structure for forward flow regeneration;

FIG. 12 is a schematic illustration of trap muffler apparatus similar toFIGS. 3 and 4 except showing a plurality of in line traps;

FIG. 13 is a schematic illustration similar to FIG. 12 with the tubularshutter valve assembly switched opposite from its configuration in FIG.12;

FIG. 14 is a cross-sectional view of a trap muffler apparatus similar toFIGS. 3 and 4 except having a segmented trap and downstream poppetvalves used in the regeneration system;

FIG. 15 is a cross-sectional view taken along line 15--15 of FIG. 14;

FIG. 16 is a cross-sectional view taken along line 16--16 of FIG. 14;

FIG. 17 is a schematic illustration of an alternate embodiment trapmuffler apparatus with a segmented trap and an axial tubular shuttervalve assembly used in the regeneration system;

FIG. 18 is an exploded perspective view of the tubular shutter valveassembly of the apparatus of FIG. 17;

FIG. 19 is a perspective view of a disk shutter valve of the type usefulin the apparatus of FIG. 12;

FIG. 20 is a cross-sectional view of trap muffler apparatus similar toFIG. 14 except trap segments are mounted on a rotatable carousel formovement to a single regeneration station;

FIG. 21 is a cross-sectional view taken along line 21--21 of FIG. 20;

FIG. 22 is a cross-sectional detail showing cooling mechanism for apoppet valve assembly;

FIG. 23 is an end view of the apparatus of FIG. 22;

FIG. 24 is a cross-sectional detail of an alternate embodiment ofcooling mechanism for a poppet valve assembly;

FIG. 25 is a cross-sectional detail showing an alternate embodimentcooling mechanism for a poppet valve assembly; and

FIG. 26 is a cross-sectional view of a trap muffler apparatus similar toFIG. 14 except having a single full face regeneration system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1, apparatus in accordance with the presentinvention is designated generally by the numeral 20. Apparatus 20includes a trap muffler device 22 with an external trap bypass line 24and regeneration mechanism 26. Engine 28 has exhaust gases which aredirected through line 30 to a valve 32. Valve 32 is shown as a four-way,two-position valve, but may be any appropriate valve which provides theproper function. Exhaust gases are directed through trap muffler device22 until trap 34 is sufficiently loaded with particulates so that unlessit is regenerated, it could significantly effect engine performance orcause thermal damage to the filter during subsequent regenerationthereby resulting in trap failure. When that level of loading isdetermined by regeneration mechanism 26, valve 32 is switched so thatexhaust gases are directed through bypass line 24 which bypasses trap34, but does not bypass at least one of the acoustic elements in trapmuffler device 22.

Trap muffler device 22 has a housing 36 with inlet and outlet tubes 38and 40, respectively. Housing 36 has at least one acoustic element andpreferably more than one. In this regard, device 20 in FIG. 1 is shownto have a resonating chamber 42 near the inlet end of housing 36 and aresonating chamber 44 near the outlet end. Trap 34 is mounted inexpansion chamber 46 between resonating chambers 42 and 44. Exhaustgases entering housing 36 flow along a first fluid flow path throughinlet 38 to expand into resonating chamber 42 and/or expansion chamber46. The gases then must pass through trap 34 to outlet tube 40. As thegases flow through outlet tube 40, they can expand into resonatingchamber 44.

Bypass line 24 is in fluid communication with chamber 46 of housing 36such that exhaust gases flow thereinto downstream from trap 34, butupstream from at least one acoustic element, namely resonating chamber44. Thus, when valve 32 is switched so that exhaust gases are directedalong a second fluid flow path through tube 24, they do not interferewith the regeneration of trap 34, but sound created by them is muffledwithout introduction of a second muffler housing since the gases aresubjected to at least one acoustic element between the location at whichthey enter housing 36 and the outlet from it.

Construction of a trap muffler device using a ceramic filter element forthe trap is well known to those skilled in the art. Appropriate detailsmay be found in U.S. Pat. No. 4,851,015 which patent disclosure isincorporated herein by reference. Line 24 can be attached to housing 36in a fashion known to those skilled in the art, such as by providing anopening in the housing wall and welding a tube extending through theopening to the housing wall to prevent leakage. The tube wouldnecessarily include an open end and/or a plurality of smaller openings48 in the side wall of the tube which is located within housing 36 asshown in FIG. 1.

The term acoustic element is recognized by those skilled in the art toinclude reactive, passive absorptive, or dissipative attenuation. Areactive acoustic element is understood to mean anything designed toattenuate sound by phase cancellation due to reflection so that onesound wave cancels another by approaching the other (e.g., a resonatingchamber). Reactive attenuation is contrasted with passive, absorptiveattenuation where amplitude is damped with interaction with anothermedium. The previous methods are further contrasted with dissipatedattenuation (e.g., a labyrinth or an enlarged chamber) wherein sound isdecreased primarily by expansion, and not so much by phase cancellationor absorption.

A trap may take any of the following representative forms: ceramic ormetallic wall flow filter (e.g., extruded monolith, extruded segmented,paper corrugated and wound monolith, or paper corrugated and woundsegmented); ceramic or metallic foam filter (e.g., monolith orsegmented); wound ceramic or metallic fiber yarn filter; woven ceramicor metallic yarn filter; woven ceramic or metallic yarn pleated filter;or non-woven ceramic or metallic pleated paper filter. The FIGURES showand the description is written in terms of using an extruded monolithicceramic wall flow filter element. As indicated, the other filter formsmay be used with change only necessary to the degree known to thoseskilled in the art. The present ceramic filter element is mounted in acan which is welded or otherwise affixed to housing 36. A ceramic filterof the type useful with respect to the present invention is commerciallyavailable from Industrial Ceramics Department, Ceramics ProductsDivision, Corning Glass Works, Corning, N.Y. 14830 or NGK Insulators,Ltd., 2-56 Suda-Cho, Mizuho-ku, Nogoya 467, Japan. In addition, a fullerdiscussion of the mounting and use of this type of ceramic filter withrespect to a regenerative exhaust filtering system may be found in U.S.Pat. No. 4,851,015.

Over time, trap 34 collects an increasing mass of particulates from theexhaust of engine 28. To maintain filtration effectiveness withoutcreating an excessive backpressure to the engine, trap 28 must beperiodically regenerated. Regeneration mechanism 26 is shown in FIG. 1.It is understood, however, that the regeneration mechanism could beremote from housing 22 so that trap 34 would be periodically removed andregenerated at a remote site. In this regard, see U.S. Pat. No.4,899,540 which is herein incorporated by reference.

Referring to regeneration mechanism 26 in FIG. 1, a proper combinationof differential pressure or pressure drop across trap 34, air mass flowrate into engine 28, and air temperature near trap 34 results in afactor which is proportional to captured particle mass. The factor isindependent of air flow to the engine, engine speed, and exhausttemperature. The factor can be calculated as follows: ##EQU1## wherek=factor, C=constant, ΔP=pressure drop across trap, Q=air mass flowrate, T=absolute temperature near inlet end of trap, and where x, y, andz have predetermined values in a range from 0.1 to 2.0. Since the factork increases monotonically with time and does so without great variation,various values of k relate to various weights of accumulated particulatemass accumulated in the trap. Therefore, a mass value and, consequently,a value of k can be chosen as a threshold for initiating regeneration ofthe trap. Different values of accumulated mass are appropriate fordifferent sizes of ceramic filters as used with various engines andexhaust systems. An appropriate value is readily determinable to thoseskilled in the art.

The values for pressure drop, air mass flow rate, and absolutetemperature near the inlet end of the trap are measured as indicatedhereinafter. The values are raised to exponents designated x, y, and z.The exponents have predetermined values which are determinable by thoseskilled in the art using a least squares or other equivalent method formatching the curve of an equation to empirical data. Similarly, theproportionality constant, C, is determinable by those skilled in the artin a similar fashion. The empirical data is obtained for a particularengine and exhaust system, usually for a particular vehicle.

It is understood that the present method for determining when toregenerate the trap is representative and that other methods may as wellbe used. A fuller discussion of the present method is provided in U.S.patent application Ser. No. 07/399,859 filed Aug. 29, 1989, which isincorporated herein by reference.

With further reference to FIG. 1 and the method described hereinbefore,air mass flow rate is measured by a sensor 50 near the air intake toengine 28. The sensed measurement is communicated to processor unit 52via line 54. Sensor 50 is a type known to those skilled in the art, suchas a hot-wire probe or a Venturi style flow meter. Pressure sensors 56and 58 measure pressure upstream and downstream of trap 34 so that apressure drop can be obtained. Sensors 56 and 58 communicate necessaryinformation to processor unit 52 via lines 60 and 62, respectively.Temperature at the upstream face of trap 34 is measured by thermocouple64 which communicates with processor unit 52 via line 66. At theappropriate time based on the calculation of factor k, heating element68 is turned on via line 70. Combustion air is provided by source 72 ascontrolled via line 74 with air directed upstream of trap 34 via line76. At a time preferably before heating element 68 is turned on, valve32 is switched via line 78 to direct the exhaust gases to bypass trap34. After a flame front has been initiated during regeneration, heatingelement 68 is turned off. When the flame front completely burnsaccumulated particulates from one end of trap 34 to the other,combustion air is turned off and valve 32 is again switched so thatexhaust gases are again directed through trap 34 rather than bypassingit.

An alternate embodiment trap muffler apparatus 20' with external bypassis shown in FIG. 1A. Apparatus 20' is the same as apparatus 20 exceptvalve 31 is a tubular valve assembly of a type apparent from discussionhereafter instead of a four-way, two-position valve 32, and bypass line24' is connected via pipe 23 to resonating chamber 42' instead of beingconnected to the four-way, two-position valve 32.

Trap muffler apparatus having an internal bypass in accordance with thepresent invention is shown in FIG. 2. Apparatus 80 includes a trapmuffler device 82 with regeneration mechanism 83. Regeneration mechanism83 is the same as regeneration mechanism 26 of apparatus 20 in FIG. 1.Trap muffler device 82 has a housing 84 with an inner canister 86.Housing 84 includes an inlet 88 connected with a first fluidcommunication line leading to the engine and an outlet 90 connected to asecond fluid communication line leading to atmosphere. Housing 84 has aplenum chamber 92 near the inlet end and a resonating chamber 94 nearthe outlet end. Chamber 96 is formed between chambers 92 and 94 andcontains inner canister 86. Inner canister 86 has a solid wall 98 and isheld spaced from the outer solid wall of housing 84 by a spider orspacer brackets 100 near the opposite ends of inner canister 86. Innercanister 86 includes a resonating chamber 102 near the inlet end.

Trap 104 is fixed to inner canister 86 and located between resonatingchambers 102 and 94. The ceramic element of trap 104 has upstream anddownstream faces. Exhaust gases from the engine are directed throughinput 88 which bypasses plenum chamber 92 and opens into resonatingchamber 102 and expansion chamber 96. After passing through trap 104,the exhaust gases exhaust through outlet 90 which opens into resonatingchamber 94, before leading to atmosphere. When trap 104 requiresregeneration, the valve is switched so that the exhaust gases aredirected to bypass inlet 106 leading to plenum chamber 92 which is influid communication with an annular space between the walls of housing84 and inner canister 86. The annular space opens into chamber 96downstream from trap 104 so that the exhaust gases may flow throughoutput 90 while having the benefit of the sound muffling of resonatingchamber 94. Thus, apparatus 80 provides for bypass of trap 104, and doesso by directing the exhaust gases into housing 84 to bypass the upstreamface of the ceramic element and flow in a flow enclosure between housing84 and the side of the ceramic element, as opposed to apparatus 20 wherethe exhaust gases are directed into housing 36 downstream from trap 34.Each system has advantages. For example, housing 36 of apparatus 20 canhave a smaller diameter with bypass tube 24 taking on whatever shape isnecessary to package the system relative to a particular vehicle.Apparatus 80 has a larger relative diameter than apparatus 20, but trap104 can be affixed by those skilled in the art to wall 98 of innercanister 86 so that the bypassed exhaust gases provide a peripheralheating for the ceramic filter of trap 104. In this way, regenerationmay be enhanced since the heating element need not provide all theenergy to ignite a flame front. Furthermore, there would be lesslikelihood of heat loss around the periphery so that the flame front canburn farther through the ceramic filter and more evenly thereby reducingthermal stress.

Although not shown in FIG. 2, it is noted that valve 87 could bereplaced with a disk shutter valve similar to that shown in FIG. 19 byreplacing end wall 103 of inner canister 86 with the disk shutter valve.It is also noted that the acoustic elements need not be a part of thehousing, but may be formed in the tubes upstream or downstream of thehousing which direct he exhaust gases to the housing, such acousticattenuation apparatus being disclosed in U.S. patent application Ser.No. 07/260,818, filed Oct. 21, 1988, herein incorporated by reference.

An alternate embodiment of apparatus 80 is shown in FIG. 2A as trapmuffler apparatus 80". Apparatus 80" is similar to apparatus 80 exceptvalve 87 and bypass inlet 106 are replaced by a tubular valve assembly89 apparent in detail from disclosure hereinafter. Valve assembly 89 incombination with the structure previously disclosed in FIG. 2 wouldpreferably have three sets of openings 91, 93, and 95. When openings 93and 95 are in registration in the fashion of a tubular valve assembly asdisclosed hereinafter, exhaust gases would flow into resonating chamber102" and expansion chamber 96" for appropriate sound attenuation andfiltering. When openings 93 and 95 are closed for flow and openings 91are in registration, exhaust gases would flow into plenum chamber 92" inorder to bypass trap 86".

Another embodiment of trap muffler apparatus with internal bypass inaccordance with the present invention is shown in FIGS. 3-9. Apparatus108 in FIGS. 3 and 4 has a trap muffler device 110 with regenerationmechanism 112. Regeneration mechanism 112 is the same as that describedwith respect to apparatus 20 in FIG. 1 and does not need furtherexplanation. Trap muffler device 110 has a housing 114 with an outercylindrical wall 116 and end baffles 118 and 120 and an interior baffle122. The baffles forming walls extend generally transversely relative tosaid cylindrical wall. Baffles 118 and 120 provide end closures forcylindrical wall 116. Interior baffle 122 provides a wall such that aresonating chamber 124 is formed between baffles 120 and 122. Each ofbaffles 118 and 120 are formed to have portions of tubes 126 and 128,respectively, extending outwardly. Tube 126 provides input from theengine to trap muffler device 110 and tube 128 provides output. Trap 130is mounted in chamber 132 formed between baffles 118 and 122. Trap 130is annular with a cross-sectional shape in the form of a ring in orderto receive a portion of a tubular shutter valve assembly 134 through thecenter.

Trap 130 is shown in more detail in FIGS. 5 and 6. Trap 130 includes anannular shaped ceramic element 136. An annular shaped filter as opposedto a cylindrical or other uniform cross-sectional shape, may result inmore uniform velocity of flow-through and more uniform loading. Asindicated earlier, a ceramic element is commercially available andpreferably is an extruded ceramic which is fired so that the primarycrystalline component is cordierite. With respect to element 136,parallel channels 138 run the full length of the element. The walls 140of channels 138 are porous thereby allowing them to function as filtermedia. Opposite ends of adjacent channels are plugged with a ceramicmaterial 142. This forces exhaust gases as illustrated in FIG. 7 throughwalls 140 so that soot 144 is collected on the walls. Heat resistantmaterial 144 provides both an intumescent, cushioning function and afire retardant, heat resisting barrier between element 136 andsurrounding walls. Material 144 is wrapped about the outside wall ofelement 136 and also about the inside wall. The ends of material 144 arespaced from the ends of element 136 so that a sealing material 146, suchas a compressible braided rope of fiberglass, may be fitted therein.Interior and exterior metallic walls 148 and 150 retain material 144 inplace and have ends turned over element 136 so as to compress sealingmaterial 146 and hold all parts together to form a modular trap. Trap130 is welded or otherwise affixed to wall 116 of housing 114. U.S. Pat.No. 4,851,015 provides a fuller discussion of creating a trap module,although the present disclosure is the first to recognize advantagesfrom using an annular trap.

The tubular shutter valve assembly 134 provides a mechanism fordirecting exhaust gases through trap 130 or directing the exhaust gasesto bypass trap 130. Assembly 134 includes an outer cylindrical tube 152and an inner cylindrical tube 154. Outer tube 152 has the same innerdiameter as outlet tube 128 and extends from spider bracket 156 which isattached to wall 116 of housing 114, to a distance spaced upstream fromthe upstream end of trap 130. The upstream end of outer tube 152 isclosed with a cover 158. Outer tube 152 is supported by spider bracket156 and annular trap 130.

Inner tube 154 extends from inside outlet tube 128 to near cover 158.Inner tube 154 has an outer diameter which is slightly less than theinner diameter of outer tube 152. A precision relationship between thediameters of the tubes helps to reduce leakage. A certain amount ofleakage, however, is acceptable since leakage will only cause a slightlyincreased demand for combustion air during regeneration or a slightlyreduced trap collection efficiency.

Inner tube 154 is supported by outlet tube 128 and tube 152. Inner tube154 is not attached to but has a sliding relationship with baffle 122.Inner tube 154 has a plurality of openings 160 in the region where innertube 154 is contained within resonating chamber 124. Openings 160 allowexhaust gases to expand into the resonating chamber for the purpose ofmuffling sound.

Each of inner and outer tubes 152 and 154 have upstream and downstreamsets of elongated openings 162 and 164, respectively, to form upstreamand downstream valves relative to the ceramic filter element. That is,the openings are regularly spaced about the periphery of each tube witheach opening spaced from an adjacent opening sufficiently far so thatinner tube 154 can be rotated to cause the openings to move into and outof registration with the openings in outer tube 152. In addition, theopenings are arranged so that if openings 162 are out of registration,openings 164 are in registration and vice versa. In this way, whenopenings 162 are out of registration with one another, as shown FIG. 3,exhaust gases (see arrows 165) are through trap 130 and openings 164 forexhaust past resonating chamber 124 to outlet tube 128. When openings162 are in registration within one another, so that openings 164 are outof registration with one another, exhaust gases (see arrows 167) aredirected through openings 162 and for a reason to be further discussedhereinafter, the exhaust gases bypass trap 130, to flow past chamber 124to outlet tube 128. Each set of openings 162 and 164 should provide aflow-through area at least as great as the cross-sectional area of innertube 154 so that recognizing the openings will still cause somerestriction, it will not be an excessive or undue restriction.

As shown in FIG. 8, the moving mechanism for inner tube 154 with respectto outer tube 152 and outlet tube 128, includes a slot 166 in outlettube 128 through which a lever 168 which is attached to inner tube 154protrudes. An actuator 170, such as an electrical solenoid, is attachedto lever 168 and is controlled via line 172 leading to themicroprocessor or other control mechanism. When lever 168 is movedcircumferentially one way or the other, tube 154 rotates appropriatelyto achieve the alignment or misalignment of openings 162 and 164 aspreviously discussed. The outlet end 174 of inner tube 154 has a taper176 so that as the exhaust gates flow to atmosphere any leakage throughslot 166 is aspirated through the taper from outside to inside.

As shown in FIG. 9, a relief valve 178 may be installed in cover 158 sothat if regeneration fails so that the trap remains loaded, the reliefvalve can open as exhaust pressure builds, thereby avoiding damage tothe engine. Also, when trap 130 approaches its loaded condition justprior to regeneration, any pressurizing surge of exhaust gases may berelieved to bypass filter 130. Relief valve 178 is depicted as a taperedplunger 180 biased with a spring 182 against a bracket 184 fastened tocover 158.

As indicated previously, when the particulate soot cake has accumulatedto satisfy the logic of the regeneration system so that it is determinedthat regeneration of the ceramic filter element is necessary, theregeneration process begins. Apparatus 20 and apparatus 80 in FIGS. 1and 2 show forward regeneration. That is, the heater is on the upstreamside of the ceramic filter element so that particulates are ignitedinitially at the upstream end and the flame front burns toward thedownstream end. U.S. Pat. No. 4,851,015 and U.S. patent application Ser.No. 07/399,859 disclose forward flow regeneration in detail.

Apparatus 108 in FIGS. 3 and 4 show regeneration mechanism 112configured for reverse flow, that is, flow in a direction opposite tothe flow of the exhaust gases through the ceramic filter element.Although the apparatus shown in FIGS. 3-4 show an acoustic element otherthan the expansion space in the chamber in which the trap is located, itis understood that such acoustic element is not necessary for thefiltration and regeneration functions. With reference to FIG. 4, in areverse regeneration configuration, heating element 186 is positionedbetween the downstream end of trap 130 and baffle 122. Thermocouple 188is in the region between heating element 186 and the downstream end oftrap 130. Combustion air is inserted into chamber 132 at a tube 190 in aregion downstream from heating element 186. If a heat reverser element192 is used, as shown in FIGS. 3 and 4, it is positioned between heatingelement 186 and combustion air entry tube 190. In a reverse regenerationconfiguration, the heating reverser is advantageously on the clean sideof trap 130 so that it is unlikely to capture particulates or debrisand, therefore, not become an exclusive restriction to flow. Thefunction of heating reverser 192 is disclosed in greater detail in U.S.Pat. No. 4,878,928, herein incorporated by reference. It is noted thatalthough heating reverser 192 is preferable, it is not needed.Regeneration mechanism 112 is otherwise the same as regenerationmechanism 26 and can be triggered by monitoring a factor k as describedadequately hereinbefore. In this regard, it is further noted, however,that some other triggering logic may as well be used.

In use, as depicted in the flow chart of FIG. 10, once it is determinedthat regeneration is necessary, as indicated in box 194, the upstreamand downstream valves as represented by sets of openings 162 and 164 areswitched so that exhaust gases 167 are directed to bypass trap 130.Then, as indicated by lines 196 and 198 leading to boxes 200 and 202,combustion air and the heating element are turned on. One may be turnedon before the other. A flame front will not be ignited, however, untilthe pressure of combustion air builds sufficiently to flow as indicatedby arrows 204 in a reverse direction against incoming exhaust gases 167.Both remain on as indicated by lines 206 and 208 leading to box 210,until combustion occurs. As indicated by line 212 leading to box 214,the heater is turned off sometime after combustion begins as may besensed by the thermocouple. After combustion has been completed, asindicated by line 216 leading to box 218, combustion air is turned off.As indicated by line 220 leading to box 222, the valves are thenswitched so that exhaust gases 165 once again are directed through trap130 as indicated in FIG. 3.

Several advantages are realized with reverse regeneration relative toforward regeneration. Consider first forward regeneration. The heater asshown in FIGS. 1 and 2 is nearest the lightest deposits of particulateson the filter (see FIG. 7). As the flame burns in a forward directionalong the filter element, combustion air can pass through the filterwalls before getting to the flame and, consequently, not only is thecombustion air less accessible to combustion, but it also tends to coolthe walls upstream of the flame. The combustion air that reaches theflame drives heat into the wall. As a consequence, a fairly high heatgradient between the region where the flame has burned and the regionwhere the flame is burning can be developed. If the flame prematurelyquenches, the heaviest deposits at the downstream end remain. Thus, theheater must heat the upstream end sufficiently to ignite the lightestdeposit and if the flame quenches prematurely, the greatest depositsremain.

Consider now reverse regeneration. The heater is located at thedownstream or clean side of the trap. The heater is nearest the heaviestdeposits of particulates. Combustion air is more available forcombustion since after passing through the filter wall, it flows towardparticulate deposits. Rather than driving heat into the wall, it takesheat away from the wall. The thermal gradient is less than in the caseof forward regeneration and the consequent tendency to crack the ceramicis reduced. The thickest deposits are burned first so that over heatingis much less likely particularly in view of the combustion air tendingto move heat away from the filter walls. If the flame front is quenched,the lightest deposits remain rather than the heavier deposits. Comparedto the forward regeneration situation, the filter begins the next cycleat a lower level of remaining particulates which allows for lowerpressure drops across the trap and lower temperatures duringregeneration, all of which further leads to lower cracking tendency. Ifany ash is dislodged from the walls of the trap by shock or vibration orcombustion air, it tends to be removed from the apparatus through thebypass flow path, something not possible with forward regeneration sincedislodged ash cannot move against the air flow or through the ceramicwalls. Thus, for the reasons given, reverse regeneration results in manyadvantages.

Nevertheless, a forward regeneration configuration is also possible withapparatus using the tubular shutter valve assembly as shown in FIG. 11.Apparatus 224 includes trap muffler device 226 with regenerationmechanism 228. Regeneration mechanism 228 is the same as regenerationmechanism 26 of FIG. 1. Trap muffler device is the same as trap mufflerdevice 110 of FIG. 3, except disk shutter valve 230 is provided betweentrap 232 and upstream openings 234 of tubular shutter valve assembly 236and openings 240 are formed so that they are always open regardless ofwhether openings 234 are open or closed. Depending on the particularconstruction of disk shutter valve 230, tubular shutter valve assembly236 may or may not be formed at the upstream end similar to thatdescribed with respect to FIGS. 3 and 4. In fact, in FIG. 11, diskshutter valve 230 is attached to inner tube 152'" while outer tube 154'"is not attached to the disk valve. Outer tube 154'" includes an upstreamportion 235 which is supported by a spider 233 and inlet tube 126'".Spider 233 extends between portion 235 and wall 116'". Portion 235includes openings 231 which are inside housing 114'" and upstream ofcover 158'" and are always open and which also includes openings 234which are available to be opened or closed as inner tube 152'" isappropriately moved.

The thermocouple, heating element, heating reverser, and combustion airinlet of regeneration mechanism 228 are located between disk shuttervalve 230 and trap 232. Regeneration mechanism 228 functions shuttervalve 230 in conjunction with tubular valve assembly 236. That is, whenupstream openings 234 are closed, disk shutter valve 230 is open anddownstream openings 240 are open so that exhaust gases are directedthrough openings 231 and trap 236 and out downstream openings 240. Whenupstream openings 234 are open, disk shutter valve 230 is closed so thatexhaust gases are directed to bypass trap 232 and trap 232 can beregenerated. Openings 240 remain open so that combustion gases which arepressurized to a level greater than engine exhaust gases can exhaust. Itis noted that a Venturi nozzle 237 can be provided in the inner tube oftubular valve assembly 236 which begins upstream from openings 238 andends downstream from openings 238 so that regeneration combustion gasesare aspirated and the pressure of combustion air need not be greaterthan the exhaust gases pressure during regeneration. The benefits of thenozzle, however, must be considered relative to the additional load dueto back pressure placed on the engine.

Disk shutter valve 230 is shown in detail in FIG. 19. Disk shutter valve230 includes a body 404 comprised either integrally or of separateelements affixed together in the form of a first annular disk portion406 having an outer flange 408 and an inner tubular flange (not shownsince it is behind the disk in FIG. 19). A second annular disk portion410 cooperates with first portion 406 and is fitted within a groove inouter flange 408. Second annular disk portion 410 is attached at itsinner diameter to tubular portion 412. Tubular portion 412 has the samediameter as and becomes a part of inner tube 152'" as shown in FIG. 11.Disk portion 406 is a solid sheet extending between the inner tubularflange (not shown) and flange 408 except for regularly spaced openings414. Openings 414 are spaced sufficiently far so that similarly sizedopenings 416 can be closed when second disk portion 414 is rotated so asto move the two sets of openings out of registration with one another.Flange 408 has an outer diameter only slightly smaller than the innerdiameter of wall 116'" of housing 114'" to which it is affixed by weldor other method known to those skilled.

The trap muffler apparatuses discussed hereinbefore provide for bypassduring regeneration which totally bypasses any filtering capability.Such apparatuses may not be acceptable in some applications withparticularly "dirty" engines, or sensitive applications such as citybuses, which may include all currently available diesel engines, sincesoot plumes would occur during the regeneration cycle. To overcome thisproblem, a plurality of in-line traps can be used as disclosedhereinafter.

As shown in FIGS. 12-13, apparatus 242 has a trap muffler device 244with a regeneration mechanism 246. Trap muffler device 244 has a housingin the fashion of housing 116 of apparatus 108 in FIG. 3, except it hasfirst and second expansion chambers 248 and 250. The expansion chambersare separated by a baffle 252. A first trap 254 is installed inexpansion chamber 248, and a second trap 256 is installed in expansionchamber 250. Tubular shutter valve assembly 258 has an outer cylindricaltube 260 and an inner cylindrical tube 262 as described with respect toprevious such assemblies. Outer tube 260 extends from spider bracket 264downstream from second trap 256 to a distance spaced upstream from firsttrap 254. Spider bracket 264 is attached to the outer wall of thehousing of trap muffler device 244. Outer tube 260 is supported byspider bracket 264, baffle 252, and first and second traps 254 and 256.

Inner tube 262 extends from inside the outlet tube of trap mufflerdevice 244 to a distance slightly beyond the upstream end of outer tube260. The upstream end of inner tube 262 is closed with a cover 266.Alternatively, the outer tube could extend further than the inner tubeand the cover could be on the outer tube as described with respect toassembly 134 in FIG. 3. Inner tube 262 is supported by the outlet tubeof trap muffler device 244 and outer tube 260. Inner tube 262 has aplurality of openings 268 in the region where inner tube 262 extendsthrough resonating chamber 270. Each of inner and outer tubes 262 and260 have upstream and downstream sets of elongated openings with respectto each of first and second traps 254 and 256. Upstream openings 272form an upstream valve relative to first trap 254 while second set ofopenings 274 form a downstream valve. Similarly, upstream openings 276form an upstream valve relative to second trap 256 while second set ofopenings 278 form a downstream valve. An always open set of openings 280are located between openings 274 and 276. Baffle 252 is located relativeto outer tube 260 in a region between openings 274 and 280. A wallcompletely blocking inner tube 262 is located between openings 280 and276. The various sets of upstream and downstream openings areconstructed and function similar to the upstream and downstream openings162 and 164 described with respect to tubular shutter valve assembly 134in FIG. 3. The sets of openings which function with respect to trap 254function opposite the sets of openings which operate relative to trap256. Openings 280 are always open and allow exhaust gases to escapesince wall 282 prevents the exhaust gases from continuing to flowthrough inner tube 262. Thus, when openings 272 are closed as shown inFIG. 12, exhaust gases are directed through trap 254 and into inner tube262 since openings 274 are open. The exhaust gases then flow out ofopenings 280 and into openings 276 since they are open. The exhaustgases are then directed past openings 268 leading to resonating chamber270 then exhausted from trap muffler device 244. In this way, exhaustgases may be filtered by trap 254 as described with respect to apparatus108 in FIG. 3, while trap 256 may be regenerated as described withrespect to apparatus 108 in FIG. 4. When inner tube 262 is rotated sothat opened openings 274 and 276 are closed and closed openings 272 and278 are opened, then trap 254 can be regenerated while trap 256 filtersexhaust gases, as shown in FIG. 13. Tubular valve assembly 258 isfunctioned in a fashion similar to that disclosed with respect toapparatus 108 with reference to FIG. 8.

Regeneration mechanism 246 is the same as regeneration mechanism 112,except that it is a dual system having similar components for both oftraps 254 and 256. In this regard, depending on which trap is beingregenerated, air source 284 directs air via line 286 to valve 288. Iftrap 256 is to be regenerated, valve 288 is open to allow combustion airto flow via line 290 to expansion chamber 250 as indicated in FIG. 12.If trap 254 is to be regenerated, valve 288 is open to expansion chamber248 to direct air via line 292 to expansion chamber 248. The only otherdifference of note is that pressure differentials with respect to eachtrap are compared to a single measurement of pressure as obtained frompressure sensing device 294 in resonating chamber 270.

Another embodiment of trap muffler apparatus with internal bypass whichincludes a plurality of traps so that exhaust gases are not bypassed toatmosphere without filtering, is shown in FIG. 14. Apparatus 296includes a trap muffler device 298 with regeneration mechanism 300. Trapmuffler device 298 includes a housing 302 having a wall 304 with endbaffles 306 and 308 and an interior baffle 310. The baffles are formedand fastened to wall 304 as known to those skilled in the art. Baffle306 includes a tube 312 extending outwardly which is in fluidcommunication with the engine to receive exhaust gases therefrom. Anoutlet tube 314 is supported by and fastened to baffles 308 and 310.Outlet tube 314 has a plurality of openings 316 which allow expansion ofexhaust gases into resonating chamber 318 formed between baffles 308 and310. Trap assembly 320 is installed in expansion chamber 322 formedbetween baffles 306 and 310. Trap assembly 320 includes a plurality oftraps and regeneration assemblies so that one trap may be regeneratedwhile the others continue to filter exhaust gases. As discussed morefully hereinafter, the ceramic filters of each trap are segments of anannular filter or may have some other shape. Exhaust gases andcombustion air are controlled with poppet valves with respect to eachtrap.

Trap assembly 320 has four identical filter elements 322 as shown inFIG. 16. Each element is wrapped in a heat resistant material 324 whichis the same as material 144 described earlier. The various elements 322are contained within a common container 326 which is formed to supportthem at upstream and downstream ends with collars (not shown) extendinginwardly from canister 326 and outwardly from core rod 328. A sealingmaterial (not shown) the same as material 146 is also used betweenmaterial 324 and the various collars. Canister 326 is tack welded orotherwise affixed to wall 304 of housing 302. Core rod 328 extends fromthe upstream end of trap 320 to a baffle 330 located between thedownstream end of trap 320 and baffle 310. Walls 332 which provide aflow barrier between the various traps extend from the upstream end oftrap 320 to baffle 330. Baffle 330 has a plurality of tapered openings334 for receiving poppet pistons 336. For normal flow, the valves formedby openings 334 and poppet pistons 336 are open so that exhaust gasesmay flow from inlet tube 312 through trap filters 322 and out openings334 to outlet tube 314. Once exhaust gases flow into a particular filter322, they are separated from the rest of the filters by walls 332 untilthe gases mix together again downstream from baffle 330. When theregeneration mechanism 300 closes one of the poppet valves, the trapassociated with that valve can be regenerated.

The regeneration mechanism 300 is the same as regeneration mechanism 112described with respect to FIG. 3, except it has four separatethermocouples, heating elements, and downstream pressure transducers formeasuring pressure drop across a particular filter (see FIG. 15).Regeneration mechanism 300 also provides for combustion air in adifferent fashion. Air source 338 is in fluid communication with valve340 via line 342. There is a valve 340 for each of the various poppetvalves 344. Valves 340 are normally closed and are opened by acommunication via line 346 from the processor unit of regenerationmechanism 300. Each valve 340 is in fluid communication via line 348through a check valve 350 to a chamber 352 fastened to the outer end ofbaffle 308. Poppet piston 336 extends into chamber 352 and is heldnormally open by a spring 354 in compression between the end of chamber352 near baffle 308 and the end of poppet piston 336 opposite thetapered end 356 which fits in opening 334. The shaft of piston 336 has apassageway 358 for providing fluid communication of combustion air fromair source 338 to a regenerating filter. As indicated, poppet valve 344is normally open, and when valve 340 opens the pressure in chamber 352closes poppet piston 336 and forces air through passageway 358 toprovide appropriate combustion air for regeneration. Check valve 350prevents exhaust gases from escaping into line 348. It is noted that airflowing through passageway 358 cools the poppet piston andadvantageously may allow for the use of lower temperature, lower costseals, not shown but known to those skilled in the art.

It is noted that apparatus 296 is shown configured for reverseregeneration. The poppet valves can be located at the upstream end alongwith the other appropriate regeneration mechanism elements so thatregeneration could proceed alternatively in a forward direction. Also,combustion air could be furnished in the fashion of regenerationmechanism 112 and the poppet valves could be electrically ormechanically functioned and would, consequently, not have passagewaysthrough the pistons. Apparatus 296 is particularly advantageous in thatit provides for constant filtering, as well as periodic regeneration,and it does so in a fashion which requires a pro rata percentage lesspower and air for regeneration of a single segment as compared withpower and air required if all segments were regenerated at once.

Apparatus 360 shown in FIG. 17 is another embodiment of a segmented traptype trap filter apparatus. Apparatus 360 has a trap muffler device 362with regeneration mechanism 364. Regeneration mechanism 364 is exactlythe same as regeneration mechanism 300 except tubular shutter valveassembly 366 is controlled by an electrical motor 368 via line 370leading to the processor unit. Also, combustion air is directed directlyinto the various trap chambers in a fashion similar to regenerationmechanism 112 rather than through poppet pistons.

Trap assembly 373 is the same as trap assembly 320 of apparatus 296,except tubular shutter valve assembly 373 extends through trap assembly366 rather than core rod 328 as with apparatus 296. Assembly 366 isformed to have an outer tube 372 and an inner tube 374 (see also FIG.18). Outer tube 372 extends from spider bracket 376 to inlet 378. Innertube 374 extends from outlet tube 380 to near inlet 378. Regularlycircumferentially spaced upstream and downstream openings 382, 384 areformed in outer tube 372. A small set of exhaust openings for combustionair is also formed in outer stream 372 upstream from trap assembly 386and downstream from openings 382. Outer tube 372 does not rotate.

Inner tube 374 has regularly spaced upstream and downstream openings388, 390 around three-quarters of the circumference of the tube. Asingle opening 392 for combustion air exhaust is formed centered in theregion where there are not upstream and downstream openings 388, 390 andwhere opening 392 can register with the openings 385. A wall 394 isprovided between openings 388 and opening 392. A plurality of openings396 are provided to allow exhaust gases to expand into resonatingchamber 398. A row of regularly spaced openings 400 is formed in thedownstream end of inlet tube 374 around the circumference to receive theteeth of gear 402 driven by motor 368. Regeneration mechanism 364energizes motor 368 as appropriate to rotate inner tube 374 so thatopenings 388 and 390 are in registration with openings 382 and 384everywhere except for the filter segment which it has been determined byregeneration mechanism 364 requires regeneration. With respect to thatfilter, opening 392 is in registration with one of openings 385 toprovide an exhaust for combustion air. The configuration of apparatus360 provides for reverse regeneration. For the filter segments which arenot being regenerated, exhaust gases flow through openings 388 and 382for filtration by the various segments of trap 386 not being regeneratedand then flow through openings 384 and 390 for exhaust past resonatingchamber 398 to outlet tube 380. Regeneration mechanism 364 can rotateinner tube 374 so that the appropriate filter segment can beregenerated. Alternatively, inner tube 374 can be periodically rotatedso that regeneration automatically occurs after a predetermined amountof operating time has passed.

Apparatus 404 shown in FIG. 20 is still another embodiment of asegmented trap-type trap filter apparatus. Apparatus 404 includes trapmuffler device 406 and regeneration mechanism 408. Device 406 has ahousing 410 with an outer cylindrical wall 412 and end baffles 414 and415. Each end baffle includes a tubular portion 416 and 417 extendingoutwardly. A tube 418 having an outer diameter only slightly less thanthe inner diameter of tubular portion 416 extends from portion 416through housing 410 to the upstream end of filter carousel 426. Thedownstream end of tube 418 is reduced in size and includes a pluralityof regularly spaced openings 420 around its periphery which allows adrive unit 422 having a small gear 424 fitting in a slot in portion 416to rotate tube 418 as desired.

A filtering mechanism for apparatus 404 in the form of a carousel 426includes a plurality of ceramic filter elements 428. Elements 428 areshown to be cylindrical in the FIGURES, but they could as well haveother shapes. Carousel 426 is affixed to tube 418 at elements 430 whichsurround tube 418 at opposite ends and near the mid-length of elements428. Each ceramic element 428 may be mounted in individual canisterswith appropriate intumescent material and sealing rope as adequatelydescribed hereinbefore. The various individual mountings are regularlyspaced and transversely supported as necessary, the details of which areadequately known to those skilled in the art and are not important tothe present invention. It is noted, however, that to properly direct theexhaust gases and to prevent the exhaust gases from bypassing filterelements, that tube 418 has a plurality of downstream openings 434, andthat it is necessary to provide adequate seals 436 between the carouselcanister and the filter modules on the inside of carousel 426, and alsoadequate seals 438 between the carousel canister and wall 412 on theoutside of carousel 426.

Exhaust gases flow into tube 418 and through any of the various ceramicfilter elements 428 before exhausting device 406 from openings 434 andtube 417. A wall 440 blocks the central portion of tube 418 and preventsexhaust gases from bypassing all of elements 428.

Apparatus 404 is distinguished from apparatus 296 of FIG. 14 andapparatus 360 of FIG. 17 in that it has only a single heater element 442and related elements as described hereinafter to accomplishregeneration. The idea of apparatus 404 is that periodically asnecessary the carousel is turned to sequentially move a ceramic filterelement in an appropriate relationship with heater element 442 and othermechanism to provide for regeneration of a particular ceramic filterelement while the others continue to filter exhaust gases flowingthrough them. To accomplish this, heating element 442 is supported bypiston 444 at an end 446 which includes a cylindrical skirt peripherallyenclosing heating element 442. The end of the skirt holds a seal 448which seals against the carousel. Poppet piston 444 extends into chamber450 and is held normally open by a spring 452 in compression between theend of chamber 450 near end baffle 414 and the end of poppet piston 444opposite end 446 which supports heating element 442. The shaft of piston444 has a passageway 454 for providing fluid communication of combustionair during regeneration.

Regeneration mechanism 408 in addition to the poppet valve assemblyincludes a processor unit 456. Processor unit 456 is wired to heatingelement 442 via line 458. Processor unit 456 is wired to drive unit 422via line 460. Processor unit 408 controls air source 462 via line 464.Air source 462 provides air to chamber 450 via line 466. Under a simpleform of regeneration as indicated, the processor unit provides a clockfunction which periodically rotates carousel 426. It is understood thatother control strategies could be used as well. Whenever a differentfilter element 428 is rotated adjacent to heating element 442, theheating element is turned on and after a delay combustion air is turnedon so that when the particulates ignite, the flame front can proceedthrough the filter element and regenerate it. The air and heat areturned off and when appropriate, the next filter element is rotated intoplace.

Apparatus 404 has the advantages of the other segmented traps discussed.In addition, it requires only a single regeneration heating elementrather than multiple ones.

With respect to apparatus using poppet valves, for example, apparatus296 in FIG. 14 and apparatus 404 in FIG. 20, it may be necessary asshown in FIGS. 22 and 23 to cool the chamber 468 which extends outwardlyfrom the trap muffler housing. In that case, a low temperature seal 470can be used. One way of providing cooling is to aspirate air through achamber 472 such that the air passes around and cools the walls ofchamber 468 as shown in FIG. 23. A chamber 472 would be mounted toextend outwardly from outlet tube 474 and to enclose the portion ofchamber 468 which is closest to the trap muffler housing. Openings atthe outer side of chamber 472 and at tube 474 would allow ambient air tobe drawn therethrough. The necessary aspirating effect is achieved byproviding a reduced inner tubular section 476 in the vicinity of theopenings in outlet tube 474.

An alternative cooling structure is shown in FIG. 24 where chamber 472ahas an opening adjacent to chamber 468a and furthermore has a concentricwall surrounding chamber 468a so that the air stays in contact with thechamber for a longer flow distance and therefore provides greatercooling effect.

A further alternative cooling structure is shown in FIG. 25 wherechamber 472b is mounted between the end of chamber 468b and the trapmuffler housing. In this case, chamber 468b is provided with a longerthreaded portion 480 which extends through chamber 472b and the end ofthe trap muffler housing for retention by a nut 482. Air is aspiratedthrough outer opening 484 of chamber 472b to flow around portion 480 andinto space between the reduced tubular section 476b and the outlet tube474b by passing through opening 486. In this way, portion 480 is cooledand a low temperature seal 488 can be used between chamber 468b andchamber 472b.

Apparatus 490 shown in FIG. 26 is another embodiment of a segmentedtrap-type filter apparatus. Apparatus 490 includes trap muffler device492 and regeneration mechanism 494. Device 492 has a housing 496comprising a cylindrical wall 498 with opposite end walls 500 andinterior baffle members 502. The end walls 500 and baffle members 502are fastened to wall 498 to form resonating chambers 504 and 506. Aninlet pipe 508 is attached to and held by an end wall 500 and a bafflemember 502 at the inlet end of device 492. Inlet pipe 508 is perforatedwith a plurality of first openings 510 to provide flow to resonatingchamber 504 and second openings 512 to provide flow to the expansionchamber 514 located between the interior baffle members 502. Closuremember 516 prevents fluid communication from the end of inlet pipe 508.

Similarly, an outlet pipe 518 is attached to and held by an end wall 500and baffle member 502 at the downstream end of device 492. Openings 520provide fluid communication to chamber 506.

Trap assembly 522 has a plurality of identical filter elements 524 heldin a fashion similar to trap assembly 320 shown in FIGS. 14 and 16. Eachelement is preferably wrapped in a heat-resistant material 526 which isthe same as material 144 described earlier. The various elements 524 arecontained within a common container 528 which is formed to support themat upstream and downstream ends with collars (not shown) extendinginwardly from canister 528 and outwardly from core rod 530. In this way,the upstream and downstream ends are aligned substantially alongupstream and downstream transverse planes. A sealing material (notshown), similar to material 146, is also used between material 526 andthe various collars. Canister 528 is tack welded or otherwise affixed towall 498. Core rod 530 extends from the upstream end of trap assembly522 to a spider 532 located between the downstream end of trap assembly522 and baffle member 502.

Regeneration system 494 senses differential pressure across the trapassembly and compares it to a baseline differential pressure measuredbetween resonating chamber 504 and expansion chamber 514 at a locationdownstream from the trap assembly. Fittings 534, 536, 538 providing theappropriate pressure sensing are connected via lines 540, 542, and 544to processor 546. If the ratio of the baseline pressure to the trappressure is greater than a predetermined value and the core temperatureis above a low limit, exhaust is diverted upstream from trap assembly492 and heater element 548 connected to processor 546 via line 550 isturned on. Heater element 548 heats all filter elements 524simultaneously. Temperature is measured at thermocouple 552 which isconnected to processor 546 via line 554. When temperature near theupstream face of trap assembly 528 reaches a predetermined value,combustion air is turned on. In this regard, air source 556 iscontrolled by processor 546 via line 558. Air is directed from source556 through line 560 into chamber 504. As combustion starts, timer 562times and turns off heater element 548. With regeneration completed,source 556 is turned off and exhaust is again directed through trapassembly 492.

The regeneration control logic is disclosed in more detail in U.S. Pat.No. 4,851,015 incorporated herein by reference. It is understood,however, that other regeneration control logic systems may also be used.

A ceramic filter element of the wall flow monolith type which issegmented as herein disclosed has many advantages over a non-segmentedelement of the same type. For example, a segmented monolith due to thesmaller size of the segments relative to the element as a whole can beproduced at a higher production speed because it can be processed onhigh volume, catalytic converter type production equipment. Much greatercare must be taken with respect to larger, non-segmented monolithelements. Furthermore, there is a much lower demand for larger elementsso that high speed production equipment has not been developed. Also,with respect to segment production, there is a much higher yield of goodsegments because of reduced losses in kiln firing and handling. Inaddition, there is a much shorter firing cycle in the kiln because ofthe smaller size of the segments relative to tho whole. All thesefactors lead to a significantly lower cost of a segmented monolithrelative to a non-segmented element of the same size.

There are still additional advantages. Because of the smaller size ofsegments, they have a higher thermal shock resistance. Since all theembodiments of the present disclosure use segments which are notcemented together, but are rather physically separated so that exhaustflowing through one segment does not flow to a sidewardly adjacentsegment, the individual segments allow for individual regeneration. As aconsequence, segments can expand and contract individually and do nottransmit stress to one another. Regeneration durability is thusimproved.

Thus, the present invention is disclosed in a variety of embodiments.Although the various embodiments have been described in detail and theadvantages of structure and function set forth, it is understood thatother equivalents may also be possible. Therefore, if changes are madein the structure with respect to the various embodiments, especially inmatters of shape, size, and arrangement, it is understood that they tooare encompassed within the invention to the full extent extended by thegeneral meaning of the terms in which the appended claims are expressed.

What is claimed is:
 1. Apparatus for processing exhaust gases from anengine, said apparatus comprising:a housing with inlet means, outletmeans, and first and second fluid flow paths with respect to said inletmeans upstream and said outlet means downstream, said housing includinga plurality of chambers with each of said chambers being separated fromothers by a gas impervious barrier; an acoustic element within saidhousing for attenuating the sound of said exhaust gases along said firstand second fluid flow paths; means, within said housing, for filteringthe particulates from said exhaust gases along said first fluid flowpath, said filtering means including a ceramic filter element dividedinto a plurality of segments; means forming a section of said secondfluid flow path for bypassing a portion of said filtering means todirect said exhaust gases from said second fluid flow path to said firstfluid flow path; means for regenerating said filtering means, saidregenerating means including a plurality of means for heating saidsegments and a plurality of means for directing combustion air throughsaid segments, each of said chambers including one of said segments ofsaid ceramic filter element, one of said plurality of heating means, andone of said plurality of air directing means; and means for controllingsaid regenerating means and said bypassing means.
 2. Apparatus inaccordance with claim 1 wherein said bypassing means includes a firstcylindrical tube fixed with respect to one of said inlet means and saidoutlet means and a second cylindrical tube fitting in slidingrelationship with said first tube, said first and second tubes eachincluding asymmetrically spaced first and second sets of openings,respectively, said first sets of openings being upstream from saidceramic filter element and said second sets of openings being downstreamfrom said ceramic filter element, said bypassing means further includingmeans for moving said second tube so that said first and second sets ofopenings move into and out of registration together, wherein said tubescan be moved so that said segments of said ceramic filter element aresequentially bypassed to allow for regeneration.
 3. Apparatus forprocessing exhaust gases from an engine, said apparatus comprising:ahousing with inlet means, outlet means, and first and second fluid flowpaths with respect to said inlet means upstream and said outlet meansdownstream, said housing including a chamber; an acoustic element withinsaid housing for attenuating the sound of said exhaust gases along saidfirst and second fluid flow paths; means, within said housing, forfiltering the particulates from said exhaust gases along said firstfluid flow path, said filtering means including a ceramic filter elementdivided into a plurality of segments with each being separated fromothers by impermeable barriers which extend beyond said segments to awall of said chamber to form a plurality of enclosures between saidsegments and said wall; means forming a section of said second fluidflow path for bypassing a portion of said filtering means to direct saidexhaust gases from said first fluid flow path to said second fluid flowpath; means for regenerating said filtering means, said regeneratingmeans including with respect to one of said enclosures means for heatingsaid segment corresponding to said one enclosure and means for directingcombustion air through said corresponding segment; and means forcontrolling said regenerating means and said bypassing means. 4.Apparatus in accordance with claim 3 wherein said bypassing meansincludes a poppet valve assembly normally open to form a part of saidfirst fluid flow path, said poppet valve assembly being closed to directsaid exhaust gases from said first fluid flow path to said second fluidflow path.
 5. Apparatus in accordance with claim 4 wherein said poppetvalve assembly includes a piston with a stem, said air directing meansincluding a passage through said stem and said piston so that combustionair can be directed through said passage when said poppet valve isclosed.
 6. Apparatus in accordance with claim 3 wherein said pluralityof filter segments are mounted on a carousel and said regenerating meansincludes means for rotating said carousel so that a different one ofsaid segments sequentially is rotated into a position adjacent to saidheating means and said combustion air directing means so that saidadjacent segment can be regenerated.
 7. Apparatus in accordance withclaim 4 wherein said poppet valve assembly includes an actuating end andmeans for cooling a portion of said actuating end.
 8. Apparatus forprocessing exhaust gases from an engine, said apparatus comprising:ahousing with inlet means and outlet means and a chamber therebetween,said housing also having first and second fluid flow paths for theexhaust gases, said paths having a forward direction when flow proceedsfrom said inlet means upstream to said outlet means downstream; aplurality of means within said chamber for filtering particulates fromsaid exhaust gases, said chamber having a wall downstream from saidplurality of filtering means, each of said filtering means beingseparated from the others by impermeable members extending beyond saidfiltering means to said wall to form a plurality of sub-chambers; meansfor regenerating in a reverse direction from each of said sub-chamberseach of said filtering means; means for bypassing one of said filteringmeans with said exhaust gases when said one is being regenerated by saidregenerating means while allowing the rest of said filtering means toreceive the exhaust gases for continued filtering; and means forcontrolling said regenerating means and said bypassing means. 9.Apparatus in accordance with claim 8 including an acoustic elementwithin said housing for attenuating the sound of exhaust gases alongsaid first and second fluid flow paths.